Hobet- Math question

[MemphisTiger]

I'm stumped on one of my practice questions and I don't even know what to google to look it up. Can anyone give me the formula or an explanation for this problem?

If Steven can mix 20 drinks in 5 minutes, Sue can mix 20 drinks in 10 minutes, and Jack can mix 20 drinks in 15 minutes, how much time will it take all 3 of them working together to mix the 20 drinks?

A. 2 minutes and 44 seconds

B. 2 minutes and 58 seconds

C. 3 minutes and 10 seconds

D. 3 minutes and 26 seconds

E. 4 minutes and 15 seconds

The answer is A.

TIA

[nightmare, RN]

Steven can make 4 a minute.Sue 2 a minute.Jack 1.3 a minute.That's 7.3 per minute for all three of them. 20 x 7.3 = 146 .Divided by 60=2.4333 minutes.

Well that's my working on it anyway.

[MemphisTiger]

Thanks so much! It's amazing the stuff you can forget how to do...:)

[smellyacres, BSN, RN]

Anyone else remember the Boy Meets World episode with the problem like this in it? Topanga was the only one who could solve it....

Ahh, that was a good show....

But thanks, I never knew how to do that type of problem either.

[PiperDave]

Took the test today, didn't see anything like that problem on it. very straight forward basic math.